Section III - Captive Lighting Applications
Just what does all this information about algal pigments and coral pigments mean to captive stony aquarists? The book on captive stony corals that I am writing for TFH/Microcosm goes into great detail about how the spectral output of specific light bulbs correlates or matches the spectral attributes of the various coral and algal pigments. I spend very little time analyzing how the spectral output of lower temperature bulbs (for example 5,500 K and 4,200 K) correlate with algal and coral pigmentation. This is simply because they correlate very poorly. Bulbs that emit large amounts of yellow, orange and red light will not stimulate the fluorescence of the Highly Fluorescent Pocilloporin Pigments. Bulbs that do not emit significant amounts of violet/blue/green light will not be providing the main wavelengths of light that is absorbed by the algal chlorophyll_a, chlorophyll_c2 and peridinin pigments. Chlorophyll_a can absorb some red light, but the 5,500 K and 4,200 K bulbs do not emit red light of the proper wavelength.
To help clarify the situation I have grouped useable captive light bulbs into 4 basic groups or types. They are Full Spectrum Green, Super Blue, Full Spectrum Violet and Actinic (Super Violet). The Iwasaki 6,500 K is the only bulb classified as a Full Spectrum Green bulb. This bulb emits the highest percentage of its light within the green and yellow parts of the spectrum. It also emits significant amounts of violet, blue, orange and red light. About 60 % of the total light emitted by this bulb is either green, yellow or orange light. That type of light is not primarily absorbed by the chlorophyll and peridinin pigments within the algae. The bulb does however emit significant amounts of violet and blue light which are primarily useable by the algae. This bulb could use a boost within its high energy blue part of the emission spectrum around 440 nm. Many aquarists have had success with the bulb and it is definitely useable. The very strong photon flux density emitted by the bulb helps to compensate for its spectral limitations. This bulb will moderately stimulate the blue, yellow and linked red fluorescing pocilloporin pigments. Green and red fluorescing pocilloporin will be strongly stimulated to fluoresce. A moderate amount of light emitted by this bulb can be absorbed by the pink pocilloporin pigment. The 400 and 250 watt versions of this bulb are both useable for shallow water stony corals. Many aquarists will use actinic fluorescents to help balance the green/yellow appearance of the bulb. It would be better to add blue light because the bulb already emits a significant amount of violet light.
The Radium/Osram 20,000 K and Sunburst 12,000 K are both classified as Super Blue bulbs. Super Blue bulbs emit the vast majority of their light within wavelengths from 440 to 460 nm (high energy blue). They also emit small amounts of violet and green light. The narrow emission of this bulb happens to be located within an area of the spectrum where chlorophyll_a, chlorophyll_c2 and the peridinin pigments can absorb and utilize the light. The vast majority of the emitted light energy from the Super Blue bulbs is photosynthetically useable by the algae. These bulbs can actually benefit from a boost within the violet area of the spectrum. Most aquarists however will be adding daylight fluorescents to counter the very blue visual appearance of the bulbs. These bulbs will intensely stimulate the blue, green and yellow fluorescing pocilloporin pigments. Red fluorescing pocilloporin will be moderately to strongly stimulated. Super Blue bulbs only provide a weak amount of light that can be absorbed by the pink pocilloporin pigment. The 400 watt version of the Osram/Radium and the 250 watt version of the Sunburst lamps are both useable for shallow water stony corals.
The Ushio 10,000 K and Aqualine Buschke 10,000 K are Full Spectrum Violet bulbs. The spectral output of these bulbs is characterized by a large emission of violet light along with a secondary emissions of green, yellow and orange light. As Sanjay Joshi noted these bulbs trick the human eye into thinking there are emitting significant amounts of blue light. The significant violet light emission will provide plenty of light for the chlorophyll_a pigments within the algae. These bulbs will really benefit from supplemental blue light. Full Spectrum Violet bulbs will moderately stimulate the fluorescence of the green, yellow and red fluorescing pocilloporins. They will strongly stimulate the fluorescence of the blue and linked red fluorescing pigments. These bulbs only provide a weak amount of light that can be absorbed by the pink pocilloporin pigment. The 400 watt version of the Ushio and Aqualine Buschke are acceptable bulbs, while the 250 watt version of the Double Ended HQI and Aqualine Buschke are also acceptable. Actinic bulbs or Super Violet bulbs are best used as supplemental lights for bulbs that are deficient in violet light emission.
The intensity of captive light is also an important issue. Due to space limitations I can only briefly cover the subject here. Most corals imported for the captive market come from shallow water locations. This does not mean that all corals imported are bright light corals. Some of these corals will come from shaded shallow water areas and they will be low light corals. However, the majority of imported corals will be strong light corals that expect from 700 to 1,200 micro Einsteins/square meter per second. Within the stony coral book I am writing for TFH/Microcosms I have constructed guidelines for establishing different light intensities. What I have basically done is define light intensities into 4 differentlevels that are: weak light; moderate light; strong light; and intense light. As a basic guideline, strong light is typically achieved with the use of 400 watt halides. Intense light is typically achieved with the use of 1,000 watt halides. Weak and moderate light levels can be achieved with 175 to 250 watt metal halides and power compact fluorescents. There are actually quite a few low to moderate light corals being farmed within captive systems. For example, I have been farming and distributing an Echinopora lamellosa that actually prefers weak to moderate light. It develops a very nice blue fluorescing pigment in weak to moderate light, but will loose the pigment in strong light. |